This invention relates generally to the management and control of broadband integrated services performed via digital, channelized, packetized or optically coded networks, and in particular a system for organizing, interfacing, managing, loading and controlling, in real time, grouped or organized information (such as packetized data) transported through interface access devices and switches that are in compliance with domestic and international communication standards. Further, the invention relates to the deployment of signaling in a packetized network utilizing technology such as Asynchronous Transfer Mode (ATM), which maximizes utilization of components and segments of existing networks while simultaneously providing a high bandwidth platform to support commercially competitive telecommunications and information services as well as providing a bridge between various packet protocols, modulation techniques and access technologies.
Traditional U.S. long-distance and local telephone companies do not offer the enhanced data transfer capabilities that modern business operations need. They began in the 1960's with pulse coded modulation/time division multiplexing (PCM/TDM). These systems and networks typically use digitally channelized multiplexers designed to carry voice transmissions onto individual transmission interface media (e.g., copper wire, coaxial cable, optical fiber and wireless). Base services are typically provided at 64 Kbps (DS0 channels), and corporate service with T1 (1.54 Mbps) transmission speed, which is equivalent to 24 DS0 channels. In Europe and Asia the standard is E1 (2.04 Mbps) which provides for 30 DS0 channels.
The time division multiplexing (“TDM”) technique divides the data switching or transmission bandwidth of the network facility into equal sized time slots, which have the appropriate bandwidth needed to carry a telephone voice conversation. TDM generally served its purpose when the network was primarily used for standard telephone voice transmission. However, modem telecommunications networks are now being used to transmit internet protocol (IP), video, full duplex and data in addition to voice. These services are being expanded to accommodate PCS cellular services as well as traditional telephone services. Each of these applications has varying data transmission bandwidth requirements that differ from each other and from requirements associated with traditional TDM telephony. As a result, traditional narrowband digital techniques such as TDM have not been able to fully accommodate the information and data transmission requirements of broadband equipment.
Moreover, in conventional narrowband TDM telephone networks, each circuit has a fixed bandwidth. Once a voice connection is established, its bandwidth cannot be used by any other connection, whether there is any traffic flowing or not. For instance, once a voice connection is established, a bandwidth of 56 kilobits per second is allocated for voice and 8 kilobits per second is allocated for signaling, thereby consuming 64 kilobits per party for the duration of the connection. When one of the parties is listening to the other party, the listening party does not generate any traffic. Although that allocated bandwidth is not used during such silent periods, it cannot be used to transfer any other traffic. That is, the channel bandwidth is occupied and consumed whether it is being used or not. Accordingly, there is a need for a network management system that makes efficient use of available bandwidth resources by allocating and consuming bandwidth only when payload traffic is present.
Packet technologies such as Asynchronous Transfer Mode (ATM) and packet internet protocols (IP) such as IPV4 and IPV6 technologies are now being applied to the switching and transmission facilities and to the physical and logical interfaces of public networks as well as private LAN and WAN networks. For example, where TDM uses time slots to divide the bandwidth into fixed size channels, ATM uses 53 byte cells to divide the bandwidth into virtual channels. Each cell includes a header that identifies a virtual path and virtual channel to which the cell belongs. Cells are allocated to a virtual channel in response to the needs of the users sending information over the virtual channel, subject to the limits of the transmission facilities, physical interfaces and switches that carry the virtual channel.
Private communications networks have been using packetized technology and are now using Ethernet, Gigabit Ethernet, X.25, various light wave products and wireless products in addition to ATM and IP to service customers over a large geographic area. In practice, it is not cost effective for a private network operator to install its own transmission facilities between different sites. Instead, private network operators often lease transmission lines from a public carrier. As a general rule, these leased lines are dedicated and designed to provide full transmission capacity 24 hours a day regardless of actual utilization. A large network of leased lines is typically required to provide connections between sites in a private network.
Referring to FIG. 1, a typical legacy telecommunications network includes narrowband and special purpose broadband networks. In all such conventional high bandwidth networks, operators have constructed large and often specialized networks to accommodate the specific kinds of information or data transmission required by the enterprise. These included, among others, PSTN (Public Switched Telephone Networks) optimized for channelized circuits or switched voice, with overlay of packetized networks that have various protocol interfaces for handling IP internet protocols, LAN and WAN, and cable and broadcast television networks. Because many of these specialized networks were built for peak voice load conditions, the average utilization or information throughput was very low and resulted in expensive unused capacity. There is therefore a continuing interest in providing a telecommunications network that will support not only internally generated enterprise communications of diverse types but also carry communications of diverse types originated by third party subscribers.
The principal requirement of a modern network is its ability to handle video and data as well as voice traffic to and from diverse devices. One efficient way of providing such services is to logically allocate the resources of an existing network in cooperation with dynamic traffic paths provided by packetized networks. An effective arrangement is to overlay a number of logical networks, referred to herein as virtual private networks, each including nodes or switching devices and interconnecting logical links. Each virtual network forms a logical traffic path through an existing network. The logical links of the virtual networks share the capacities of physical links present in the existing physical network.
A physical network may consist of physical nodes formed by packet switches, routers, broadband interface access devices, customer-side interface access devices, physical links interconnecting the nodes and various ancillary devices. A physical link or “backbone” utilizes a transport medium such as copper wires, coaxial cables, fiber optical conductors, and/or wireless radio links, individually or in combination. In general, the physical links are arranged into trunk groups or circuit groups which extend between the physical nodes. There are access/egress interface access nodes to the physical network, to which access devices, such as telephone sets computer modems, cable modems or wireless devices are connected.
Information, whether channelized or packetized, such as voice, IP, video and data, is transported across the packet network by different transport means, for example STM (Synchronous Transfer Mode) and ATM (Asynchronous Transfer Mode).
A broadband packetized services digital network handles both data transmissions (e.g., computer) and telecommunications (e.g., telephone). This carrier service provides high speed communications to end users in an integrated way. Typically, the technology selected to deliver the service is photonic or electrical with digital or analog coding using modes such as Asynchronous Transfer Mode (ATM), or Gigabit Ethernet (Gig E), or Internet Protocol (IP), switched or multiplexed, but is not limited to these technologies. The almost universal acceptance of ATM for broadband networking is because ATM handles all kinds of communication traffic, such as voice, data, video, high quality sound and multimedia. ATM can be used in both LAN (Local Area Network) and the WAN (Wide Area Network) network environments and hence enables seamless inter-working between the two.
ATM and Gig E packet protocols transported over such media as WDM or DWDM are effective in a much wider range of communications environments than any previous technology. ATM or Gigabit Ethernet or IP generally is applied at OC48 or lower bandwidth requirements, whereas switched photonic DWDM or WDM would be more efficient at multiple OC48s or higher. This means that instead of having a proliferation of many specialized kinds of equipment for different functions it is now possible to have a single type of equipment and network that will accommodate a wide range of services.
Communication technologies have realized considerable progress and many potential applications that were not possible before are now becoming accessible and attractive. High speed traffic rates can now be sustained with very low bit error rates with the development of new transmission media, and especially optical fiber. The increasing user demand for packetized broadband communication services and for ever faster services has caused carriers to look for an integrated way of supplying these services, since operating disparate networks is very expensive.
As data transfer speeds for network communications increase, timing among network system components becomes increasingly critical. Due to the high data transfer speeds, synchronization between the network elements must be maintained to avoid quantization noise distortion and bit error rate. Conventional networks are synchronized at 4 KHz which is the standard clock frequency. Conventional 4 KHz network clocks provide an accuracy of 4.6×10−6 second per month. However, as networks are implemented with optical switching, for example OC3, OC48 and higher, the network switches run at much higher frequencies, for example 1.92–2.6 gigaHz. The optical switching devices are still being synchronized with the conventional 4 KHz network clocks which provide an accuracy of only 4.6×10−6 second per month. The disparity between the optical signaling frequency and the sampling clock frequency causes the accumulated network bit error to become very high, resulting in jitter, frame slip on video, noise distortion and delay on voice-over-IP, router delay or latency, which generally do not satisfy QoS requirements.
The accumulated bit error becomes significant and is manifested visually as frame slips or blocks missing from packet transmissions, which is commonly encountered on cable television networks. It may also be heard as a hum or echo in a normal telephone call, and as delay in voice-over-IP transmissions. If the network switches are not synchronized, the bit error rate and the packet delay become completely unacceptable for some traffic. For example, some routers may require as much as 200 milliseconds to make a routing decision, and that must be added to the response time of the signal as it propagates over the network paths. The direct result is phase jitter, packet delay and quantization distortion. These are all problematic especially for voice and video conferencing transmissions, which require the highest quality of service, where the overall packet delay must not exceed about 40 milliseconds.
A further limitation on conventional broadband networks is caused by the lack of common standards and operating rules among diverse narrowband and broadband network devices, which prevents them from communicating directly with each other by a common network protocol. The protocols of conventional network equipment are vendor specific, and such equipment is generally not certified for operation under a common set of national and international rules, for example IEEE and ITU standards. The lack of standardization among all network equipment is the direct cause of a substantial portion of noise, jitter, cell loss, phase shift, congestion, over-subscription and packet delay, thus generally degrading the quality of service performance across the network.